Put AdBlue® in your diesel tank? One wrong move could cost you thousands
Putting AdBlue® into a diesel tank, a guide by Steve Buckley, Sales Manager, Fleetmaxx Solutions Burnley
Putting AdBlue® into a diesel tank is one of those mistakes that can happen in seconds but become extremely expensive if the vehicle is started.
If you have just realised what has happened, the most important thing is simple: Do not switch on the ignition. Do not start the engine!
AdBlue® is not a fuel or a diesel additive. It belongs in a completely separate tank and is injected into the vehicle’s exhaust system. If it enters the diesel tank, it can contaminate the fuel and potentially damage the fuel pump, injectors, filters and fuel lines.
The quicker you act, the better your chances of preventing a sizeable repair bill.
What should you do immediately?
If AdBlue® has accidentally been poured into your diesel tank:
- Do not turn on the ignition. On some vehicles, switching on the ignition can activate the fuel pump and begin circulating the contaminated diesel.
- Do not start the engine. Starting it can move the mixture through the fuel system and into expensive components.
- Do not add more diesel. Adding diesel might dilute the AdBlue®, but it will not remove the contamination.
- Keep the vehicle stationary. Do not attempt to drive it to a garage.
- Tell anyone else who may use the vehicle. This is particularly important with shared fleet vehicles. Place a warning on the steering wheel or keep hold of the keys.
- Contact a professional fuel-drain or recovery service. The tank will normally need to be drained, cleaned and refilled with fresh diesel.
Catching the mistake before the engine is started can make an enormous difference.
Why is AdBlue® so damaging to a diesel fuel system?
AdBlue® and diesel perform completely different jobs.
Diesel is an oil-based fuel that powers the engine. It also provides vital lubrication for parts of the fuel system, including high-pressure pumps and injectors.
AdBlue® is a solution made from high-purity urea and demineralised water. It is used by a vehicle’s Selective Catalytic Reduction system to help reduce harmful nitrogen oxide emissions.
It is injected into the exhaust gases after combustion. It should never enter the engine or mix with diesel.
Because AdBlue® contains water and does not have diesel’s lubricating properties, it can cause:
- Corrosion inside the fuel system
- Reduced lubrication
- Damage to the fuel pump
- Blocked or damaged injectors
- Contaminated fuel filters
- Crystalline deposits in pipes and components
- Poor engine performance
- Vehicle breakdown
- A potentially substantial repair bill
Modern common-rail diesel systems work under extremely high pressure and rely on clean fuel. Their components have very fine tolerances, which means contamination can quickly become a serious problem.
What happens if you have not started the engine?
This is the best possible situation following an AdBlue® misfuelling incident.
The vehicle will still require professional attention, but the contamination may remain largely inside the fuel tank. A specialist may be able to drain and clean the tank before refilling it with fresh diesel.
There is no guarantee that further work will not be required, but leaving the ignition and engine switched off can significantly reduce the chance of the AdBlue® reaching the pumps, fuel lines and injectors.
Do not be tempted to start the vehicle to see whether it still runs. That one decision could turn a fuel-drain job into a much larger repair.
What happens if you start the engine?
Once the engine or fuel pump starts operating, the contaminated mixture can begin travelling through the vehicle’s fuel system.
Depending on the vehicle, it may reach:
- The fuel filter
- Low-pressure and high-pressure fuel pumps
- Fuel lines
- The fuel rail
- Diesel injectors
The water in AdBlue® can encourage corrosion, while the loss of lubrication may damage moving parts within the fuel pump.
AdBlue® can also leave crystalline deposits as it dries. These deposits may block filters, narrow fuel passages and interfere with injectors.
If a high-pressure fuel pump is badly damaged, it may release small metal particles into the system. In severe cases, this can mean that the pump, fuel rail, injectors and associated pipes all require cleaning or replacement.
What if you have already driven the vehicle?
If you have driven after putting AdBlue® into the diesel tank, stop as soon as it is safe and legal to do so.
Switch off the engine and do not restart it.
You should then arrange professional recovery rather than attempting to drive to a garage. The longer the vehicle continues running, the further the contamination may travel.
A qualified technician may need to inspect the tank, filter, pumps, injectors and fuel lines. The appropriate repair will depend on the amount of AdBlue® added, how long the engine ran and the design of the vehicle’s fuel system.
What are the warning signs?
A vehicle affected by AdBlue® contamination may display symptoms such as:
- Difficulty starting
- Rough idling
- Loss of power
- Engine hesitation
- Misfiring
- Unusual engine noises
- Dashboard warning lights
- The engine cutting out
However, you should never wait for these symptoms if you already know AdBlue® has entered the diesel tank. By the time the vehicle starts behaving differently, the contaminated fuel may already have circulated through important components.
Can you dilute AdBlue® with more diesel?
No. Filling the rest of the tank with diesel is not a safe solution.
Adding more diesel may reduce the concentration, but the water and urea will remain inside the tank. AdBlue® is denser than diesel and may settle near the bottom, where the vehicle’s fuel pick-up is often located.
The correct approach is to have the contaminated fuel professionally removed and the system cleaned where necessary.
Will a small amount of AdBlue® cause damage?
There is no universally safe amount of AdBlue® that can be added to a diesel tank.
The level of risk depends on:
- How much AdBlue® entered the tank
- How much diesel was already present
- Whether the ignition was switched on
- Whether the engine was started
- How far the vehicle was driven
- The design and condition of the fuel system
Even a relatively small amount should be treated as contamination. Do not take a chance with a modern diesel fuel system.
Is AdBlue® flammable?
AdBlue® is not a fuel and is not considered flammable under normal conditions.
The danger in this situation is not that the AdBlue® will ignite. The problem is that its water and urea content can contaminate a fuel system that depends on clean, lubricating diesel.
What if diesel is put into the AdBlue® tank?
Putting diesel into the AdBlue® tank is also a serious mistake.
Instead of threatening the engine’s fuel system, diesel can contaminate and damage the vehicle’s Selective Catalytic Reduction system. This may affect the AdBlue® pump, dosing equipment, injector and catalytic components.
The advice remains the same: do not switch on the ignition or start the engine. Arrange professional assistance immediately.
How can fleet operators prevent AdBlue® misfuelling?
A few straightforward controls can help businesses reduce the risk:
- Train drivers on the purpose of AdBlue® and its separate filling point
- Label diesel and AdBlue® fillers clearly
- Use dedicated, properly labelled dispensing equipment
- Never store AdBlue® in an old diesel, oil or chemical container
- Store diesel and AdBlue® equipment separately
- Include misfuelling instructions in driver handbooks
- Place emergency guidance inside fleet vehicles
- Ask drivers to report mistakes immediately without fear of blame
That final point matters. A driver who reports the mistake before starting the engine may save the business thousands of pounds.
The simple rule to remember
If AdBlue® enters the diesel tank, do not start the vehicle and do not attempt to dilute it.
Keep the vehicle switched off and arrange for professional draining and inspection. Fast action may be the difference between cleaning the tank and replacing several expensive fuel-system components.
At Fleetmaxx Solutions, we help businesses manage their diesel and AdBlue® requirements more efficiently. Through FleetBlue, we manufacture quality AdBlue® here in the United Kingdom and can supply businesses in volumes suited to their fleet, including 1,000-litre intermediate bulk containers and larger storage solutions.
If your business needs a reliable AdBlue® supply, clearer fleet controls or advice about reducing forecourt costs, please get in touch with the Fleetmaxx Solutions team.
Additional AdBlue® information you will find of interest
One of our most asked questions is “what is AdBlue®” and “what is it made of”, here we try and answer this for you.
Understanding AdBlue® and its regulations in the UK has become essential for fleet operators, businesses, and vehicle owners.
Determining how much AdBlue® to use depends on various factors. Here’s some general guidelines to help you.
Is AdBlue® ISO 22241 important?
Discover why ISO 22241 compliance is essential for protecting your fleet’s SCR systems and ensuring reliable emissions performance.
The short answer is no, AdBlue® is not toxic. However, there are still considerations when handling and storing it properly.
AdBlue® quick enquiry
This article provides general information and should not replace advice from the vehicle manufacturer, a qualified technician or a professional fuel-recovery specialist. If misfuelling occurs, do not operate the vehicle and seek professional assistance immediately.
